Tools for turning and tools for milling are provided with a single or several coated cutting inserts. As shown in FIG. 1, a coated cutting insert 1 has a rake face 2 which is located on side where swarf 6 of a work material 5 is lifted at the time of cutting processing, and a flank face 3 which is located on the side which faces the work material, and the portion which corresponds to a ridge where rake face 2 and flank face 3 cross is referred to as a cutting edge 4, and becomes the center point of application for cutting the work material.
The edge of this coated cutting insert must be replaced when the lifetime is expired. In the case of an insert with only one cutting edge, the insert itself must be replaced. In the case of a coated cutting insert having several cutting edges, however, the direction can be changed several times on the same datum plane, i.e., an unused cutting edge is positioned in a cutting position, so that the insert can be used with another cutting edge. In some cases, the insert is reattached to another datum plane, so that an unused cutting edge can be used with this support.
At the site of cutting work, however, in some cases, a coated cutting insert is replaced or changed in direction before the cutting edge is used. This happens because it is not recognized whether or not the cutting edge has been used when the edge is replaced or the direction of the cutting edges is changed. Accordingly, it is necessary to carry out the above described operation after it has sufficiently been confirmed whether or not the cutting edge has been used.
As a method for easily identifying a cutting edge after use, a coated cutting insert where the rake face and the flank face have different colors has been proposed (Japanese Unexamined Patent Publication 2002-144108 (Patent Document 1)). Concretely, this coated cutting insert has a configuration where a base layer having wear resistance, referred to as anti-friction coating layer, is formed on a substrate, and an indicating layer is formed of a material that is easily worn on the flank face.
However, although a coated cutting insert having this configuration has a function of giving caution about whether or not the cutting edge has been used, the indicating layer that has been formed on the flank face easily adheres to a work material, and therefore, because the indicating layer adheres to the surface of the work material, or because cutting processing is carried out with the edge in an uneven state with work material adhering to the indicating layer, such a problem arises that the appearance and surface smoothness of the work material after cutting are poor.
Patent Document 1: Japanese Unexamined Patent Publication 2002-144108